Laser Induced Breakdown Spectroscopy Based on Single Beam Splitting and Geometric Configuration for Effective Signal Enhancement

Abstract

A new laser induced breakdown spectroscopy (LIBS) based on single-beam-splitting (SBS) and proper optical geometric configuration has been initially explored in this work for effective signal enhancement. In order to improve the interaction efficiency of laser energy with the ablated material, a laser beam operated in pulse mode was divided into two streams to ablate/excite the target sample in different directions instead of the conventional one beam excitation in single pulse LIBS (SP-LIBS). In spatial configuration, the laser beam geometry plays an important role in the emission signal enhancement. Thus, an adjustable geometric configuration with variable incident angle between the two splitted laser beams was constructed for achieving maximum signal enhancement. With the optimized angles of 60° and 70° for Al and Cu atomic emission lines at 396.15 nm and 324.75 nm respectively, about 5.6- and 4.8-folds signal enhancements were achieved for aluminum alloy and copper alloy samples compared to SP-LIBS. Furthermore, the temporal analysis, in which the intensity of atomic lines in SP-LIBS decayed at least ten times faster than the SBS-LIBS, proved that the energy coupling efficiency of SBS-LIBS was significantly higher than that of SP-LIBS.

Advances in explosives analysis—part II: photon and neutron methods

“…Using a CO 2 laser as the second pulse efficiently reheats the plasma plume through an inverse Bremsstrahlung absorption process, without increasing the quantity of ablated mass [166,182]. More recently a geometry-dependent, singlebeam-splitting LIBS approach obtained signal enhancement (~5×) resulting from the angle and energy of the second beam and not the timing [183]. Remote filamentation-induced breakdown spectroscopy (R-FIBS) uses ultrashort fs lasers to induce a filament in the atmosphere over distances of up to a kilometer, with no need for focusing optics [168].…”

Time-resolved characteristics of laser induced breakdown spectroscopy on non-flat samples by single beam splitting

“…It has been reported that the thickness of absorption zone is inversely proportional to the angle of incident laser beam. 19 In the single beam mode, a large incident angle of around 85 gives rise to a thin absorption zone. It follows from the inset on the le that the incident path of beam I indicated by the pink dash line passes through a less area of the absorption zone.…”

“…[12][13][14][15][16][17] Another method employed for signal enhancement is the double-pulse LIBS with a single laser system, which emerged as a promising technique due to the advantages of the signicant enhancement effect, low cost, and simplicity. [18][19][20][21] This approach has been already proposed earlier by Antony et al, where two laser pulses generated from one laser focus on the same small surface area of specimen of interest. 18 A double-pulse fs-LIBS with collinear conguration by utilizing a single laser system was reported and the enhancement factor of 4 was observed for Zn atomic lines.…”

“…However, when the laser energy was set below 60 mJ, an increase in signal intensity of emission spectra was not obtained. 19 Although the double-pulse LIBS technique with single laser system has been proven to be effective in laboratory, the complex ambient conditions introduce extreme constraints from the point of view of applicability, which has a negative effect on LIBS measurement. 22 Among the environmental factors, sample surface is one of our most concerns since it brings a signicant impact on the sensitivity and reliability of the LIBS technique, especially for the detection and analysis of trace elements.…”

“…Different from the single-beam-splitting method noted above, an obvious enhancement effect on emission intensity is obtained when a 1064 nm Nd:YAG laser with pulse energy below 60 mJ is utilized in our case. 19 In order to better understand the physical mechanisms behind the signal enhancement, the time-resolved characteristics of laser-induced plasma obtained by single-beam-splitting LIBS and by traditional single beam LIBS are comparatively investigated.…”